I have my .48 idealing perfectly, but when I throttle up full bore it stalls. I can increase throttle slowly without stalling.
I have increased, and decreased the high speed neddle valve only to either not ideal properly, or will run rough.
Any ideas??
Thanks

Do you have the engine manual??? In the back of my engine manual for my os it has a detailed chart showing how to set up the needle valve and airbleed screw. For the high speed needle, close it all the way, then open it 2 turns. Start the engine and close it about half a turn, you should be abelt o hit full throttle here. Leave it at full throttle, without the glow plug ignitor on, and slowly close the valve and listen to the rpm's, as soon as they drop off, open the valve 15-30 degrees. This should allow instant transition from idle to full. What kind of engine do you have, a .48 sounds lie it is an MDS, i don;t know if these have an airbleed screw like OS. If it does the website should have a downloadable manual that'll show you how to adjust the airbleed.

To set the transition from idle to fullthrottle is not that hard. A great deal depends on which engine it is and the type of carb.

If it's an air-bleed type w/single needle or a 2-needle carb. The engine manual will tell you, or someone here will know. A lot of the current engines use a 2-needle set-up which are easy to work with. I have 3, MDS and 1, K&B w/2-needle carbs, and all work great when set up properly.

The second nedle is usually placed inside the throttle arm. Look for a recessed screw 'inside' the arm (it will be a slotted screw,not a phillips).

If you can, post a couple pics of the carb. It would help a lot.

If it is an MDS .48.......this is what you need to do..........
Close the throttle all the way. Gently turn the low-speed needle in, 'clockwise', until you meet some good resistance. DON'T crank it in , or you may do some damage.
Now, with the throttle still closed, open the low-speed needle 2 1/2 turns 'counterclockwise'. You will need to watch the blade of the screwdriver as you turn it to count the turns. This is a good starting out setting.

When setting 2-needle carbs to run, ALWAYS tune the high-speed needle valve first for optimum performance and rpm. When you have this, THEN play with the low-speed needle to set the transition, not the idle.

If the carb has an 'idle stop screw', turn it out as far as you can w/o it falling out, you don't really need it. Set your idle by adjusting your linkage to the throtle arm so you have the smallest opening in the carb throat as necessary to keep the engine running. You could also use the throttle trim switch on the radio to do this. My MDS .40 idles great with the opening in the carb at only about 1mm from being closed completely. My low-speed (I like to call it 'transition' needle) at 2 turns.

I set-up my throttle linkage, radio throttlr trim lever in a way that allows me to cut the engine totally for shut down. By moving the throttle to idle, then moving the trim lever to full down, kills the engine.

Food for thought ...
What per cent fuel are you using ? Sometimes , if the fuel is not high enough in nitro content , it will do the same ..
The best way to tell if you fuel is not high enough in nitro pre centage , is start her up ( cold start ) , then immediately after starting , pull the glow ignitor off . If it remains running , then your ok and I would suggest doing as stated above . BUT....
If it dies on you .... then up the per cent of the nitro fuel by 5 per cent .
Again , this test is from a cold start ...

Here is a link to the [link=http://horizon.hobbyshopnow.com/ProdInfo/Files/MDSmanual.pdf]MDS .48 Engine Manual[/link]. Hope this helps. Now here is a question for you all because my O.S. .40Fx sometimes doesn't run properly. On my twin engine boat, i use a .40la, and a .40Fx. The Fx should have more power than the .40 la, but when i run both on 15%fuel the la outperforms the Fx. The Fx runs fine for a few mins and will go up to ful lthrottle for about 20 secs then the rpm's drop and it slowly bogs down. If i idle it, it runs fine again and then after about 30 secs if you open up the throttle it'll die. This has been getting better over time, as i put more hours on it. I bought this engine used, so it may not have been broken in properly. However, if i run 10%fuel the Fx doesn't have any of these problems until about maybe 2 mins of running WOT. But if i back off it's fine, and doesn't die at all. I have posted asking about this b4, in the engines forum, and I get the normal, check the fuel tank, check the lines, check this check that, and it's none of those normal remedies. I would rather run 15% or even higher for speed, but 10% can suffice. Anyone have any suggestions???

If it seems to run fine for the first minute or two, and then slows down, it is probably overheating from being too lean. It may only be a couple of clicks worth, but that is enough to do it.

Richen it up just a tad and try it again.

The FX should have more power than the LA. If you are trying to run them synced, the settings will be different for each.

For engines of different types, I would suggest syncing by rpm, and not by sound.

I flipped my Airforce yesterday and now it has the same symptoms. I cnaged glow plugs, dried out the engine, drained teh fuel. Still does. it. Any idas?

Thanks for all the tips.
After a FEW attempts of correctly setting the neddles, it appears to throttle up fine now.
By the way, I'm using 15% nitro fuel.
Thanks again
Sirwalter

The fx is getting better as i put more fuel through it, and yes i initially synced the engines by rpm. The la still just barely pulls the fx around when it starts to bog down. Both of these engines got dumped when i rolled my boat, i simply over primed it by about 15 cranks to get fuel and oil in the engine and they both run the way they did before. I am, thinking about rebuilding my engine pod so that one is a puller and one is a pusher, the engines would be inline so that if the fx keeps acting the way it does it won;t affect the course as much. Also when one runs out of fuel or if it cuts i don't have to do big circles to shore.

It could be that you still have some moisture somewhere. Unless you bake the engine in the oven at 100 degrees for about an hour, it will take some time for all the water to evaporate out of it. Even if you use WD40 to displace the water. There are a lot of nooks and crannys that moisture can hide, including the carb.

I would remove the engine, take off the head and backplate and let it dry out for a couple days.

Another thing to consider is that when it flipped, you may have gotten a tear or pinhole in the fuel or pressure line(if using pressure). Also check the fuel line inside the tank for the same thing. Better yet, just replace it. Check the brass tubes for cracks also.

These may seem like simple things, but this turns out to be the problem for a not-so-right running engine, regardless if it was tossed in the drink.

I would check these things out before assuming you ruined the engine.

Thanks Pro. I will give that stuff a try.

I have found that sometimes a pinhole leak in the fuel line will make the engine run bad. It is one thing you could check. Especially if the boat started it all of a sudden. Does not hurt to try a different glow plug.

As a matter of fact, I did have an open vent that I'm sure was causing some of the problem.
Everything seems to A-OK now.

Mine was doing similar things - turned out to be some debris in the carb - fuel inlet side